Contact resonance atomic force microscopy using long elastic tips.

In this work, a new theoretical model for contact resonance atomic force microscopy, which incorporates the elastic dynamics of a long sensing tip is presented. The model is based on the Euler-Bernoulli beam theory and includes coupling effects from the two-beam structure, also known as an 'L-shaped' beam in the literature. Here, high-accuracy prediction of the sample stiffness, using several vibration modes with a relative error smaller than 10% for practical working ranges, is demonstrated.

Experimental validation of contact resonance AFM using long massive tips.

In this work, we present an experimental validation of a new contact resonance atomic force microscopy model developed for sensors with long, massive tips. A derivation of a new technique and graphical method for the identification of the unknown system parameters is presented. The technique and contact resonance model are experimentally validated.

Scanning speed phenomenon in contact-resonance atomic force microscopy.

This work presents data confirming the existence of a scan speed related phenomenon in contact-mode atomic force microscopy (AFM). Specifically, contact-resonance spectroscopy is used to interrogate this phenomenon. Above a critical scan speed, a monotonic decrease in the recorded contact-resonance frequency is observed with increasing scan speed.

Quantitative Contact Resonance Force Microscopy for Viscoelastic Measurement of Soft Materials at the Solid-Liquid Interface.

Viscoelastic property measurements made at the solid-liquid interface are key to characterizing materials for a variety of biological and industrial applications. Further, nanostructured materials require nanoscale measurements. Here, material loss tangents (tan δ) were extracted from confounding liquid effects in nanoscale contact resonance force microscopy (CR-FM), an atomic force microscope based technique for observing mechanical properties of surfaces.

Vibrational shape tracking of atomic force microscopy cantilevers for improved sensitivity and accuracy of nanomechanical measurements.

Contact resonance atomic force microscopy (CR-AFM) methods currently utilize the eigenvalues, or resonant frequencies, of an AFM cantilever in contact with a surface to quantify local mechanical properties. However, the cantilever eigenmodes, or vibrational shapes, also depend strongly on tip-sample contact stiffness. In this paper, we evaluate the potential of eigenmode measurements for improved accuracy and sensitivity of CR-AFM.

Characterizing the free and surface-coupled vibrations of heated-tip atomic force microscope cantilevers.

Combining heated-tip atomic force microscopy (HT-AFM) with quantitative methods for determining surface mechanical properties, such as contact resonance force microscopy, creates an avenue for nanoscale thermomechanical property characterization. For nanomechanical methods that employ an atomic force microscope cantilever's vibrational modes, it is essential to understand how the vibrations of the U-shaped HT-AFM cantilever differ from those of a more traditional rectangular lever, for which analytical techniques are better developed. Here we show, with a combination of finite element analysis (FEA) and experiments, that the HT-AFM cantilever exhibits many more readily-excited vibrational modes over typical AFM frequencies compared to a rectangular cantilever.

Hydrodynamic corrections to contact resonance atomic force microscopy measurements of viscoelastic loss tangent.

We present a method to improve accuracy in measurements of nanoscale viscoelastic material properties with contact resonance atomic force microscope methods. Through the use of the two-dimensional hydrodynamic function, we obtain a more precise estimate of the fluid damping experienced by the cantilever-sample system in contact resonance experiments, leading to more accurate values for the tip-sample damping and related material properties. Specifically, we consider the damping and added mass effects generated by both the proximity of the cantilever to the sample surface and the frequency dependence on the hydrodynamic loading of the system.

Characterization of silver-gallium nanowires for force and mass sensing applications.

We investigate the mechanical properties of cantilevered silver-gallium (Ag(2)Ga) nanowires using laser Doppler vibrometry. From measurements of the resonant frequencies and associated operating deflection shapes, we demonstrate that these Ag(2)Ga nanowires behave as ideal Euler-Bernoulli beams. Furthermore, radial asymmetries in these nanowires are detected through high resolution measurements of the vibration spectra.

Flexural vibration spectra of carbon nanotubes measured using laser Doppler vibrometry.

Laser Doppler vibrometry is used to measure the thermal vibration spectra of individual multiwalled carbon nanotubes (MWNTs) under ambient conditions. Since the entire vibration spectrum is measured with high frequency resolution, the resonant frequencies and quality factors of the MWNTs are accurately determined, allowing for estimates of their elastic moduli. Because the diameters of the MWNTs studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate values for the smallest diameter nanotube or nanowire whose vibration can be measured in this way.